1. Field of the Invention
The present invention generally relates to a method and a system for promoting scanning speed, and more particularly to a method and a system for promoting scanning speed by adjusting system clock to change the data generated rate corresponding to the transmission rate of the transit interface.
2. Description of the Prior Art
Scanners are widely applied for the ability of generating digital representation of the information comprised by an original. The digital representation typically processed on a host device such as computer, and through an I/O cable data is transmitted from the scanner to the computer. The data transmission rate from the scanner to the host device is depended on the communication protocol used between the scanner and the host device. Ideally, digital data transferred to the host device is produced at the same rate that the host device can accept it. Therefore, no memory buffer is required for accumulating data that is waiting for transfer. However, the digital data is usually produced at a rate quite different from the data reception rate of the host device. If the transmission rate is higher than the data generated rate of the scanner, the scanner can run in full speed with no possible loss of data. However, the data generated rate of a scanner is usually faster than the transmission rate of the host computer. Therefore, when the transmission rate is lower than the data generated rate, issues related to the efficiency of the scanning operation often arise in the scanning operation.
Besides optical resolution, the scanning speed is another essential functional criteria of scanners. The scanning speed is the time that the scanner sends back scanned image to the host device after the scanning work is started. If the transmission rate is slower, the image data will be accumulated in a memory buffer, and the memory buffer may finally get full after only a portion of the original is scanned. In order to prevent the loss of the image data, the scanning operation is halted when the memory buffer is full and, then resumed when the memory buffer is empty or available for storing more data again. In other words, when the memory buffer is full, a scanning module driven by a motor is stopped and moved backward for a predetermined number of steps, due to the first few step motions of the scanning module being usually quite shaky and unstable that is caused by mechanical vibrations resulting in affecting the quality of the output in that period. Then, the scanning module is forwarded from there when the data accumulated in the memory buffer is transmitted to the host device. The processes of stopping and restarting the scan are alternatively performed till the scanning operation is completed. This method of preventing the loss of image data is useful, but it may cause the scanning of an original to take a long time because the scanning is stopped and restarted repeatedly.
The procedure of moving the scanning module backward and forward or, in other words, the procedure of stopping and restarting the scanning module is so called a smearing or start-stop process. This procedure might help to solve the problem of unstable scanning module or memory buffer full but it takes time to move the scanning module backward and forward, which may reduce the overall scanning speed of the scanner. Besides the start-stop process, in order to overcome the problems associated with data transfer from the scanner to the computer due to the varying transmission rate of the computer, lots of methods have been proposed. The increase in size of the memory buffer is one of the methods. The scanning of the original is thereby not affected by the varying capability of the computer to receive data. Enlarging memory buffer is quite straight forward and easy but with some drawbacks, that is, it also increases cost and complicates the manufacture of a scanner. Moreover, it may not really solve the problem when a high-resolution scan is performed, which can generate a huge amount of image data within a very short period of time, and it is not feasible to simply increase the memory buffer size to alleviate the problem.
A scanner with fast scanning speed can shorten the time while scanning of an original, speed up and increase work efficiency. Thus, it is imperative to develop a method and a system which reduces the possibility of memory buffer being full leading to the reduction of the time wasting on start-stop processes and thereby promoting the scanning speed without requiring the increase in size of a memory buffer.